Many industrial water systems, e.g., cooling towers, boilers, forming section of a paper making process, and waste treatment systems use chemical treatment products for improved energy efficiency, waste reduction, asset protection, and improve product quality. Typical treatment products for industrial water systems control scaling, corrosion, fouling, foaming, odor formation, and microbiological growth. These treatment products comprise polymers and other materials and are known to people of ordinary skill in the art of a particular type of industrial water system.
To achieve optimum performance from the chemical treatment products introduced into an industrial water system requires a feed strategy. For example, a typical industrial water system as used in cooling towers will employ a control system that can be set up to feed treatment product based on either a bleed/feed mechanism, where the action of blowdown triggers a chemical feed pump or valve that feeds treatment product; or, in the alternative, the control system feeds treatment product based on timers using a “feeding schedule,” or flow meters on the make-up water line trigger the pumping of treatment product based on a certain amount of make-up water being pumped. A limitation of these control methods is that none of these systems measure the treatment product concentration directly online, so if there is a mechanical problem, for example, if a pump fails, a drum empties, or high, low or unknown blowdown occurs, system volume changes or makeup water quality changes; the correct treatment product concentration is not maintained. Because this problem is common, typically industrial water systems are either overfed to ensure the level of treatment product in the system does not drop too low as a result of high variability in product dosage, or the treatment product is unknowingly underfed. Both overfeeding and underfeeding of treatment product are undesirable due to cost and performance drawbacks.
One method of combatting these undesirable drawbacks is by blending an additive blend that includes an inert fluorescent chemical and an active ingredient blended in known proportion to one another, adding the additive blend to the industrial water system, and monitoring the fluorescent signal of the inert fluorescent chemical using a fluorometer. The typical industrial water system may require several additive blends, which would make up an additive package. As a person of skill in the art readily recognizes, the typical additive blend or package for an industrial water system must first be formulated, then blended and inventoried prior to its shipment and use by the end user. Because of the endless possible design variations of industrial water systems, there may be as many additive blends and packages as there are industrial water systems. Furthermore, a process can exhibit dynamic variations, e.g., changes in makeup water composition that feeds a cooling tower, seasonal changes, etc., requiring reformulation of the blend to achieve optimum performance. The typical industrial water system may require several of these additive blends to function properly, and each can be properly dosed into the industrial water system using a control apparatus such as TRASAR® Technology or 3D TRASAR® Technology, each available from Nalco Company, 1601 West Diehl Road, Naperville, Ill. 60563. All of these additive blends are typically formulated using one or more of several common raw materials.
Those who produce additive blends encounter several issues when blending (“make-clown” or “making-down”) a new additive blend or package. First, the cost of formulating a new additive blend or package can be expensive. Several batches may need to be blended and tested to determine the optimal ratio of additives. Not only does the industrial water system require that formulation be done when new, but the formulation will likely need adjusting as the system ages. Such formulation and re-formulation requires significant man-hours.
Second, the make-down of additive blends and packages at full strength can be dangerous. Several of the additives require the use of formulation aids such as strong acids or bases in order to get the active ingredients to dissolve. The additives, when blended at full strength, may release heat or fumes. Additionally, because the blend will likely sit in storage for a lengthy period of time, the blend may require the addition of costly halogen- or photo-stable dyes as tracers.
Systems for blending and feeding liquid chemicals are generally based on one or more sensor technologies such as load cell, level sensor, and volumetric measuring devices to measure the amount of chemical dispensed. In some cases a characteristic measurement of the liquid is used to determine the mixture concentration. For example, U.S. Pat. No. 5,522,660, to O'Dougherty et al., disclosed the use of a conductivity probe to monitor the concentration blend of DI water mixed with a concentrated chemical.
Further, U.S. Patent Application Publication No. 2009/0139545, to Rowlands et al., discusses the use of fast acting solenoid values with a control algorithm to inject super-concentrated chemicals into a water conduit for vehicle washing. The amount of chemical feed is controlled by the solenoid valve on/off timing sequence. Concentrated chemical is injected directly into the conduit and diluted at the point of use, thereby eliminating the need for a dilution step or mixing tank.
Thus, there is a long-felt but unmet need for more efficient delivery of additives used in industrial water systems than currently exists. Ideally, a service provider would avoid off-site formulation and blending altogether by shipping the necessary raw materials to the customer and performing the blending at the customer's site that can provide real-time adjustment and dosage control. More ideally, the make-down would not require the use of halogen- or photo-stable dyes. Even more ideally, the raw materials would be directly injected into the industrial water system at optimum levels without the need for make-down. The invention at hand satisfies this long-felt but unmet need.